Question: Why did Mark E. Petersen say that blacks would go the the Celestial Kingdom as servants?

Not everything said by a leader of the Church is considered doctrine

Elder Mark E. Petersen said, " If that Negro is faithful all his days, he can and will enter the celestial kingdom. He will go there as a servant, but he will get a celestial resurrection. He will get a place in the celestial glory." Therefore, do Mormons consider God to have an "equal heaven" for all races?

First, of all, not everything said by a leader of the Church is considered doctrine. So just because an apostle says something, does not make it binding doctrine, especially if he was speaking at a Convention of Teachers of Religion, as Elder Petersen did. For more information, please read:

"Approaching Mormon Doctrine", Newsroom, The Church of Jesus Christ of Latter-day Saints.

We believe revelation is continual, and we do not claim to have all the answers now, nor did we claim to have all the answers in 1952

We believe God will yet reveal many great and important things. For more information, please read:

The 9th Article of Faith

It is important to understand that the term "servant" was not uniquely applied to black people

It is assumed by most, based upon Elder Petersen's statement, that white people would not go to the Celestial Kingdom as servants. However, we must examine DC 132꞉16

Therefore, when they are out of the world they neither marry nor are given in marriage; but are appointed angels in heaven, which angels are ministering servants, to minister for those who are worthy of a far more, and an exceeding, and an eternal weight of glory.

As you can see, the Doctrine and Covenants makes no mention that the servants are limited to any race. Blacks and whites will serve alongside each other.

Even Petersen's view that blacks can only serve alongside whites as servants in the Celestial Kingdom has been contradicted by almost every president of the Church since Joseph Smith

It is interesting that critics will take a quote and think it represents Mormon Doctrine no matter how clear it contradicts other statements. We believe in the law of multiple witnesses. One single person expressing his view was never meant to be taken as doctrine. See DC 6꞉28

Here are some quotes from Mormon leaders that say blacks will be able to receive ALL blessings, including that of the highest degree of the Celestial Kingdom

In regards to black people, Joseph Smith taught,

"They have souls, and are subjects of salvation."
—Teachings of the Prophet Joseph Smith, selected by Joseph Fielding Smith, (Salt Lake City: Deseret Book Company, 1976), 269. ISBN 087579243X

Brigham Young, who clearly believed in the "Curse of Cain," said

"when all the rest of the children have received their blessings in the Holy Priesthood, then that curse will be removed from the seed of Cain, and they will then come up and possess the Priesthood, and receive all the blessings which we are now entitled to."
—quoted by the First Presidency, August 17, 1949.

Wilford Woodruff said,

"The day will come when all that race will be redeemed and possess all the blessings which we now have"
—quoted by the First Presidency on August 17, 1949.

George Albert Smith reiterated what was said by both Brigham Young and Wilford Woodruff in a statement by the First Presidency on August 17, 1949

David McKay taught,

"Sometime in God's eternal plan, the Negro will be given the right to hold the Priesthood. In the meantime, those of that race who receive the testimony of the Restored Gospel may have their family ties protected and other blessings made secure, for in the justice of the Lord they will possess all the blessings to which they are entitled in the eternal plan of Salvation and Exaltation."
—(Mormonism and the Negro, pp. 23)

In reference to black people, Apostle Joseph Fielding Smith taught,

"Every soul coming into this world came here with the promise that through obedience he would receive the blessings of salvation. No person was foreordained or appointed to sin or to perform a mission of evil. No person is ever predestined to salvation or damnation. Every person has free agency."
—Joseph Fielding Smith, Doctrines of Salvation, Vol.1, p. 61

In 1972, Harold B. Lee said,

"It's only a matter of time before the black achieves full status in the Church. We must believe in the justice of God. The black will achieve full status, we're just waiting for that time."
—Kimball, Lengthen Your Stride, working draft chapter 20, page 22; citing Goates, Harold B. Lee, 506, quoting UPI interview published November 16, 1972.

Finally, Elder Petersen voted to give the priesthood to the blacks in 1978. He was part of the Quorum of The Twelve, who unanimously accepted the revelation extending the priesthood to all blacks. By voting to extend the priesthood to the blacks Elder Petersen's vote also allowed them to receive Celestial Marriage, which was the only thing keeping them from progressing beyond the status of ministering angel.

Official Declaration—2

So regardless of what Elder Petersen's views were in 1952, when Elder Monson eulogized him, he had changed his views and in fact was instrumental in removing the priesthood ban.

Finally, it is a long shot to say because someone is running for president who belongs to a church that is headed by someone who gave a eulogy for someone else almost 30 years ago who 30 years prior to that made a racist comment, that therefore that person holds the same racist views. It is a stretch to say the least.

Notes

Question: Why did Mark E. Petersen say that blacks would go the the Celestial Kingdom as servants?